The 2-alkyl-1,4-butanediols, especially 2-methyl-1,4-butanediol, have a variety of uses. For example, they can be cyclized to the corresponding 3-alkyltetrahydrofurans. Amongst other uses, 3-alkyltetrahydrofurans can be copolymerized with tetrahydrofuran to form polyether glycols, and those glycols can be used in preparing polyurethane elastomers. In the past, 2-alkyl-1,4-butanediols have been prepared by a variety of techniques. For example, they have been prepared by the reduction of itaconic acid. They have also been prepared by the hydroformylation of 1,4-butenediol followed by hydrogenation of the hydroformylation reaction product (believed to be 2-formyl-1,4-butanediol) as described by Copelin in U.S. Pat. No. 3,859,369. In addition, they have been prepared by catalytic hydrogenation of 1,4-butynediol or 1,4-butenediol in the presence of an aldehyde as disclosed in my U.S. Pat. No. 590,312.
While the prior art methods are useful, they are not without their disadvantages. Itaconic acid and the acetylene-based chemicals used in prior art processes are expensive, and there is thus a need for a process which can be operated at a lower cost. In some of the prior art processes, production of 2-alkyl-1,4-butanediols is accompanied by the production of 1,4-butanediol. Those prior art methods yield a greater quantity of 1,4-butanediol than the 2-alkyl-1,4-butanediols. For example, the process disclosed and claimed in my U.S. Pat. No. 4,590,312 gives a diol mixture having a maximum 2-alkyl-1,4-butanediol content of 15 percent by weight. While that may at times be the desired result, at other times it is desirable to prepare mixtures of 2-alkyl-1,4-butanediols and 1,4-butanediol which contain more of the former than the latter.